<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>半圆</title>
		<style>
			div{
				background: red;
				margin: 30px;
			}
			div:nth-of-type(1){
				width: 100px;
				height: 50px;
				border-radius: 50px 50px 0 0;
			}
			div:nth-of-type(2){
				width: 100px;
				height: 50px;
				border-radius: 0 0 50px 50px;
			}
			div:nth-of-type(3){
				width: 50px;
				height: 100px;
				border-radius: 0 50px 50px 0;
			}
			div:nth-of-type(4){
				width: 50px;
				height: 100px;
				border-radius: 50px 0 0 50px;
			}
		</style>
	</head>
	<body>
		<div></div>
		<div></div>
		<div></div>
		<div></div>
	</body>
</html>
